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 Post subject: Half Ropes.....
PostPosted: Wed Nov 25, 2009 10:36 am 
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Joined: Wed Nov 25, 2009 10:28 am
Posts: 49
Location: Jol-burg
Real Name: Craig de Villiers
Hi everybody!!

I have a hypothetical situation....

Say I happened to be somewhere in the wilderness, and there happened to be a beautiful crag, with perfect bolts all the way up. I happened to have my climbing shoes, a harness, JUST enough quick draws for the route, and a partner to belay me. Unfortunately all I have with me is one of my trad half ropes.

The question is: Can I use a half rope for a sports route?? theoretically it should be more than able to take the weight in a fall, so what makes it a half rope?

Shot!

d0nK3y


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 Post subject: Re: Half Ropes.....
PostPosted: Wed Nov 25, 2009 11:00 am 
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The answer is NO.
You cannot use a half rope as a single.

Half ropes are designed to work together. Both absorb energy in the case of a lead fall even if cliped into different points.

Also: Never clip half ropes into the same 'biner (as you would do with double ropes)
The impact force generated and absorbed is ment to be seperated between the 2 ropes. When you clip both ropes the absorbtion within the 2 ropes increases the shock load on the specific piece of gear.
Think breaking one match, and breaking 2 matches.
Thus, when using 2 half ropes for sport climbing, clip the ropes alternately into the 'draws. Never both ropes into the same 'draw.

So, in short, use gear what it is desingned for.


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 Post subject: Re: Half Ropes.....
PostPosted: Wed Nov 25, 2009 11:29 am 
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Joined: Sat Apr 30, 2005 8:31 am
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Location: Montagu
Real Name: Justin Lawson
Well put Hann
Further info from a rope manufacturer website:

Image

Half ropes, with regard to strength and weight, lie between single and twin ropes. They only offer standard safety when they are used as a pair. But here you have the choice between twin rope technique, where both ropes run parallel through the protection and half rope technique, where the «left» and «right» ropes run separately through different protection points. This technique allows friction to be reduced in the case where protection points are widely spread and reduces impact force. This is of benefit when climbing traditionally protected routes. A belay method which enables the independent control of each rope must be used. Half ropes are tested singly with a 55 kg mass and must withstand five standard falls. They come in diameters from 8-9 mm and weigh 42-55 grams per meter. In single strand form they are suitable to belay two seconds.

Twin (Double) ropes must only be used in pairs and are clipped together into each piece of protection, as with single rope technique (= Twin rope technique). The two ropes offer >redundancy and thus, increased safety in the case of shock loading over a sharp edge. They are therefore especially suited for alpine climbing or demanding routes where retreat
may be necessary. They offer the highest safety margin and allow full length rappels. With diameters from approximately 7.5-8.5 mm and a weight of between 38-45 grams per
meter they are, together, about as heavy as the heaviest >single ropes. With standard testing the ropes must withstand 12 falls with an 80 kg mass.

Single ropes are the most common type of ropes used. Depending upon diameter and length they can be used for most conditions. The main advantage is simple handling. A disadvantage is that only routes up to a half rope length high, with subsequent lowering or rappelling, can be climbed. Single ropes come in diameters of approximately 9.4-11 mm and weigh between 57-82 grams per meter. Single ropes, withstand at least five falls with an 80 kg mass

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 Post subject: Re: Half Ropes.....
PostPosted: Wed Nov 25, 2009 11:32 am 
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Joined: Tue Apr 24, 2007 1:59 pm
Posts: 722
Well, hypothetically speaking - you could try and let us know?

No but seriously, not a good plan. Top rope on one half, yes.

Why would you theoretically only have one of your trad half ropes?

Another question: What if you're climbing a route that looks like below, and you peel off after climbing to point A, with rope X clipped to all the pieces below, and rope Y not clipped to anything at all? I've done this before to save rope drag later on the pitch, but it makes me moer-of-a nervous. I also saw the photo of Gosia doing the same on the cover of the newest SAMountain Sports. The half rope should (and does) hold, just like you were using it as a single, right? Wrong?

<Attachment should be here>


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 Post subject: Re: Half Ropes.....
PostPosted: Wed Nov 25, 2009 11:51 am 
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Joined: Tue Sep 06, 2005 11:44 am
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Pierre,

A good question to which I've never seen a satisfactory reply.

I've taken to climbing with a Joker + a half. Using the Joker in situations as you describe.

For those not familiar with a Joker: It is a 60m 9.1mm single rope.
It is a pain to switch leads though if the half is 50m.


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 Post subject: Re: Half Ropes.....
PostPosted: Wed Nov 25, 2009 12:41 pm 
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Posts: 39
This never made sense to me. In most cases when climbing on half ropes you will fall on the highest piece of gear and that will take the full impact. Of course if that then fails you have a backup with the other rope and since most of the energy of your fall has hopefully been absorbed that rope only needs to take out what energy is left. Only if you happen to have two pieces at about the same height will you load them both. Look at the diagram Justin put up. On the half rope diagram as he is about to clip the right hand rope if he falls he will fall on the left rope only. Am I missing something?


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 Post subject: Re: Half Ropes.....
PostPosted: Wed Nov 25, 2009 2:33 pm 
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Joined: Fri Dec 15, 2006 12:32 pm
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Location: Cape Town
Real Name: Willem Boshoff
carl, you are right. hann, you're not. rope clipped to the top piece takes all the impact and unless it breaks there is nothing else to it. half ropes are more likely to break than single ropes simply due to the elemental design but will it break? i think it is highly unlikely since i do not know of any half ropes breaking when used as such. otherwise i won't use it for trad or anything else for that matter.

but for heaven's sake just use it as per the manufacturers specs okay? no hypothetical experiments needed.


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 Post subject: Re: Half Ropes.....
PostPosted: Wed Nov 25, 2009 4:20 pm 
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Joined: Tue Nov 29, 2005 2:07 pm
Posts: 149
Location: somerset-west
Real Name: phlip olivier
Is the concern not that 'it may get cut' rather than 'it may break'?


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 Post subject: Re: Half Ropes.....
PostPosted: Wed Nov 25, 2009 4:29 pm 
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Joined: Tue Jul 05, 2005 1:15 am
Posts: 49
Location: Ladismith WC
Real Name: Jan Viljoen
It seems that the terminology varies somewhat regarding double, half and twin ropes. I have it as follow:

Twin ropes are ALWAYS to be clipped in pairs into EVERY runner. The only advantage to Twin Ropes is that they are thin and light to carry (shared between two) and they can be tied together for full length abseils. (This system is almost unknown in SA I'd reckon.)

Half or Double ropes are what most of us use on trad, usually two 9mm's where the one is clipped primarely to your left and the other to your right to reduce rope drag. They can however be clipped together into the same runner if you climb a straight line. (Using two single ropes in this setup should however NOT be clipped into the same runner)

Single ropes I think everyone knows these by now - used as a single line, mostly on sport or trad crack lines.

Carl, your theory is (unfortunately!) correct. However, it's very unlikely that a half rope will break, I think the best is to avoid running it out on one line. I don't like the idea of the other rope being a "backup" either, if you're about to attempt that monster route that wanders around a lot and has very long runouts I think the safest will be to use two single ropes, as long as you don't clip them together ever! When caught by both ropes running through your top runner the reduced stretch will rip your gear and break your back!

Happy tradding!
Jan


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 Post subject: Re: Half Ropes.....
PostPosted: Thu Nov 26, 2009 8:35 am 
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Jan,

I may be wrong, but:

Half ropes are also never to be clipped into the same biner.
I've seen many traddy do this, but have read in the past as stated in my first post:

If two half ropes takes the same impact force.
Both ropes only stretch with half the load, thus having less shock absorption.
Thus, if you have 2 ropes, stretching half as much as they should you are in effect doubling the shock load on the point.

In my amateur, common-sense-physics mind it makes perfect sense.
And like I said, I’ve read this on a manufacturers leaflet, but will be hard pressed to remember which one.


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 Post subject: Re: Half Ropes.....
PostPosted: Thu Nov 26, 2009 9:49 am 
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Joined: Sat Apr 30, 2005 8:31 am
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Location: Montagu
Real Name: Justin Lawson
In my amateur, common-sense-physics mind it too makes sense.

Half ropes, usually 8mm to 9mm, are used in pairs, but clipped independently to protection. These are designed to stretch one at a time to cushion the shock of a fall, just like a single rope. Clipping two half ropes to one piece doubles the amount of nylon catching the fall, increasing the impact force...
Source: Using Twin Ropes

A single rope has a lower impact force than a 1/2 rope because there is more material in the single rope to absorb energy. The skinny 1/2 rope can not dissapate as much energy and therfore transfers that energy to the pro. belay device and falling climber.
Source: Physics of Half rope method

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 Post subject: Re: Half Ropes.....
PostPosted: Thu Nov 26, 2009 10:18 am 
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Joined: Fri Dec 15, 2006 12:32 pm
Posts: 1168
Location: Cape Town
Real Name: Willem Boshoff
the published max impact force for half ropes are generally way LOWER than single ropes; typically around 6kn for halfs and 9kn for singles....... do not know if this is on account of the the lower weight used in the drop test (55kg vs 80kg) or something fundamental in the design?

anyways, the max impact force deemed to be "safe" is 12kn and most certified ropes come in well below this; if half ropes rated at 6kn are used as twin can it exceed the 12kn limit???

i have climbed with people that uses half ropes as twin on sport routes and they were happy with it. but again, i would rather stick to the manufacturers specs.


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 Post subject: Re: Half Ropes.....
PostPosted: Thu Nov 26, 2009 12:32 pm 
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Joined: Sat Apr 15, 2006 10:54 pm
Posts: 290
Real Name: CityROCK
ONE single half rope will work just fine. now read the fine print:

half ropes are meant to absorb the entire fall force individually, they are not tested in pairs. the only reason single thicker ropes even exist is that the UIAA requires a larger fall weight for a single rope. (80 kg vs. 55 kg). both the half rope and single rope have to hold the fall five times, so the only difference between half and a single is the safety margin as a half rope probably won't hold five 80 kg falls. but since you are unlikely to even take two factor two laboratory type 80 kg falls within a short period of time this is mostly an academic lab discussion.

a bigger issue is that of rope cutting. there, a single rope has a significantly higher safety margin than a half rope, as one skinny 8 mm rope is a lot more likely to be cut than a fatter 10mm, therefore the need for redundancy, a.k.a. TWO half ropes. but the UIAA stopped doing rope cut tests as it was too subjective....

another thing to consider with a single half rope is the belayer. will your belayer hold you safely with a regular belay device designed for either a single fat 10 mm rope or two 8 mm ropes?

lastly, there is the psychological element. i find that you have to trust your rope 100% in order to climb well. if there is a shadow of a doubt it will get in the way and stop you from climbing well. it's called peace of mind. and that makes all of the above a bit too academic for most people.

robert breyer
cityrock
importer of bluewater ropes; retailer of bluewater, beal, and a few others


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 Post subject: Re: Half Ropes.....
PostPosted: Thu Nov 26, 2009 2:24 pm 
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I get what you're saying about the safty factor (55 verses 80kg).

But now the question would be why are we climbing trad with half ropes instead of 2 single? Besides less weight the half rope absorbs more engergy (stretch more) than a single rope and thus places less force on your protection piece (less changce of your piece popping out)?

At least that is how I understood it. Although I regularly climb trad on two single ropes (each climber brings its own). The only reason being buying two half ropes cost a few bucks!


W :pirat:

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 Post subject: Re: Half Ropes.....
PostPosted: Thu Nov 26, 2009 3:52 pm 
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Joined: Tue Jul 05, 2005 1:15 am
Posts: 49
Location: Ladismith WC
Real Name: Jan Viljoen
About clipping both halfropes into the same runner, Hann & Justin, I get what you're saying about putting double the impact force on the pro and I agree 100%. But if I understand this correct then maybe one should consider the type of protection?

Say I have just placed a micronut (6kN?) way out to my left and I clip one of the halfropes. If my other rope is clipped way below it will not assist in catching a fall from this point. In this case I'll in fact be leading on the one half rope which I'm not supposed to do. The impact force will be very high on the rope, maybe close to breaking, but relatively soft on the nut. So now my rope might have taken a knock and I can tick off one of the five falls, but at least my fall was safely arrested.

On the other hand, having a 3.5 Cam (16kN) or a bolt I'd rather clip both ropes, the force on the ropes will be shared, so no danger of rope failure there, and my pro is unlikely to break. Unortunately more force now has to be absorbed by my belayer, knots, my body etc.

I guess one can conclude that a half rope will take a fall just as safely as a single, but it should be avoided if possible. When leading on half ropes, try not to get too much distance between your runners, so that a fall will be shared by both.


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